I am trying to install a utility sink in the basement. My question is related to draining and venting said sink.

I will attempt to describe my existing setup in order to narrow the response if possible.

I am describing from the perspective of being in the basement and looking at the wall and up from the washing machine

- Coming from the right starting at ceiling level of the basement is the obvious...the existing vent pipe for the washing machine (2")

- At the point of the vertical fall (directly behind the washing machine) from ceiling level to the washing machine their is a horizontal "T" with a vertical section of 2" DWV going to the floor

- Extending left from the "T" is a 1 1/2" DWV section approximately 15", connected to a 90 elbow going down vertically and going into the floor

- Both vertical sections go into the cement floor and appear to be drains. One is obviously the washing machine drain...described next

- The section on the right (2" pipe) has a "T" at floor level and connects to the washing machine drain pipe....which is to the right of the first vertical 2".

- The 1 1/2" DWV is un-tapped and just goes from the 90 elbow at ceiling level straight into the floor. This pipe is to the left of the 2" DWV pipe.

Ok, Now The Multi-Part Question

1. Can I safely assume the 1 1/2" DVW is connected to the drain system (visually it appears no different than the 2" washing machine drain pipe)

2. Can I tap into the 1 1/2" with a "T" and use it as the drain/vent for my Utility Sink which I want to put to the left of the 1 1/2" pipe... stating the obvious again, I will be putting a p-trap in the drain from the sink connecting to the 1 1/2" line.

The house was built in 1984 and I am located in Omaha, NE

Thanks in advance,

Jason Nager
Omaha, NE

It took me a while to untangle your question. Ya lost me with, "At the point of the vertical fall (directly behind the washing machine) from ceiling level to the washing machine their is a horizontal "T" with a vertical section of 2" DWV going to the floor."
Why is a horizontal tee on a vertical fall. Are you saying a pipe came down from the ceiling with a 2 X 1 1/2" tee and off the 1 1/2 branch of the tee it elbows back into the cement?
Then just about the time I got a 2" pipe that has a 1 1/2" next to it out comes, " to the right of the first vertical 2"pipe" We now have two two inch pipes plus a 1 1/2" one.
I guess I don't really have to know the lay out to know that you're asking me if it's OK to tee off a unknown drain line and install a utility sink on a existing drain for both a drain and a vent. Do I thinkthe1 1/2" is a drain and connected to the sewer? Yes I do, ( although in plumbing you can't "assume" anything unless it's out in the open.) do I think you can use it as a vent? Perhaps as a wet vent because if it goes into the cement there's for sure something up above using it as a drain. Would you be in code? Hell no! But it doesn't sound like your washer's in code either so it's "dealers choice" Not knowing exactly what you're working with the only way is to try it. I would cut in the tee and trap first leaving the trap full of water for a seal but open and then see if anything came shooting out of da trap when I drained the kitchen sink or took a bath. Good luck, Tom

Here is a rough sketch of the configuration...

Go for it, regards, Tom